linux-kernel - Re: [PATCH] x86: don't rely on VMWare emulating PAT MSR correctly

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Message-ID: <54906212.2010102@zytor.com>
Date:	Tue, 16 Dec 2014 08:47:14 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Juergen Gross <jgross@...e.com>, x86@...nel.org,
	tglx@...utronix.de, mingo@...hat.com, linux-kernel@...r.kernel.org,
	akataria@...are.com, jongman.heo@...sung.com
Subject: Re: [PATCH] x86: don't rely on VMWare emulating PAT MSR correctly

On 12/16/2014 01:58 AM, Juergen Gross wrote:
> VMWare seems not to emulate the PAT MSR correctly: reaeding
> MSR_IA32_CR_PAT returns 0 even after writing another value to it.
> 
> Detect this bug and don't use the read value if it is 0.
> 
> Commit bd809af16e3ab1f8d55b3e2928c47c67e2a865d2 ("x86: Enable PAT to
> use cache mode translation tables") triggers this VMWare bug when the
> kernel is booted as a VMWare guest.
> 
> Reported-by: Jongman Heo <jongman.heo@...sung.com>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> Tested-by: Jongman Heo <jongman.heo@...sung.com>

I presume cachability control is irrelevant for a VMware guest?  I'm
wondering if it would be better to just plain ignore the failure rather
than disabling PAT.

	-hpa


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